1. Field of the Invention
The present invention relates to rotary switches of the type used in electric apparatus and more particularly relates to an improved rotary switch having a rotatable disc supporting projecting cam lobes, the cam lobes being functional upon rotation of the disc to force selected electrically conductive spring contact fingers into engagement with opposed electrical terminals, the contact of the fingers and the terminals closing an electric circuit.
2. DESCRIPTION OF THE PRIOR ART
Prior art rotary switches of a type in common use are illustrated in U.S. Pat. Nos. 2,949,511 issued Aug. 16, 1960 to Glueckstein et al; 3,213,212 issued Oct. 19, 1965 to Sefton; 3,242,271 issued Mar. 22, 1966 to Stephan et al; 3,248,488 issued Apr. 26, 1966 to Stephan; and 3,308,248 issued Mar. 7, 1967 to Stephan et al. Switches of the type illustrated in the above mentioned patents are characteristic in that they are reliable and durable. However, they are subject to the disadvantage that they usually include a large number of circumferentially spaced clips individually secured around the circumference of a circular disc and a number of circumferentially spaced eyelets similarly individually secured around a circular disc. Due to the relatively large number of components comprising these switches, positioning and securing each of the components during manufacturing can be time consuming, effort intensive and costly.
More recently developed rotary switches endeavor to avoid these high production costs, but these switches prove to be unsatisfactory in other ways. Such rotary switches are shown, for example, by U.S. Pat. Nos. 3,736,390 issued May 29, 1973 to Lockard; and 3,999,021 issued Dec. 21, 1976 to Delp. These switches include a molded housing having a plurality of spaced apart side-by-side contacts supported therein and a rotatable disc supported in the housing adjacent the contacts such that the contacts are received against a planar side surface of the rotatable disc. The planar surface of the disc supports metalized electrode path patterns thereon such that rotation of the disc will result in the printed circuits providing an electrically conductive bridge between selected pairs of the contacts. A decided disadvantage of such structures is that the friction of the contacts against the electrode paths during rotation of the rotor tends to cause the metalized electrode paths to migrate in the direction of movement of the contacts as the disc rotates, eventually causing shorting between the electrode paths and resultant failure of the rotary switch.
Another structure employing a rotatable disc functional to cause an electrical connection in response to rotation of the disc is shown in U.S. Pat. No. 3,813,668 issued May 28, 1974 to Ross. The Ross patent shows a push button switch wherein a push button assembly is engageable against lugs projecting from one planar surface of a rotatable disc to cause rotation of the disc. The opposite side of the disc includes a plurality of grooves each for receiving a projecting shoulder of a metallic sensing member. The grooves each include deep cut portions and shallow-cut portions whereby rotation of the disc causes movement of the sensing members into electrical contact with a common terminal. The structure of the Ross patent is inadequate for use in connection with a rotary switch since the housing and rotor structure as well as the common terminal and sensing member arrangement facilitates only a relatively small number of switching positions, since it comprises an unduly large package, and since it is not capable of being stacked together with other similar switches.